Unimplemented status report "Unknown Status" -> "n/a"

Previously, if a plugin does not return status reports, we would say "Unknown Status", which is a bit wordy and also conflicts with the "UNKNOWN" official status, where a plugin _has tried_ to get status and is explicitly returning unknown.

"n/a" kind of implies that the very concept of health doesn't apply to some deployments, which isn't right either, but it's the least-worst thing I can think of.

internal/cli/deployment_list.go

@@ -166,7 +166,7 @@ func (c *DeploymentListCommand) Run(args []string) int {
 			}
 
 			// Add status report information if we have any
-			statusReportComplete := "Unknown Status"
+			statusReportComplete := "n/a"
 			for _, statusReport := range statusReportsResp.StatusReports {
 				if deploymentTargetId, ok := statusReport.TargetId.(*pb.StatusReport_DeploymentId); ok {
 					if deploymentTargetId.DeploymentId == b.Id {